The firing methods of automatic pistols, which are developed by and are being used in many different countries, are largely classified into two types: single action and double action. Of them, the single action consists of two steps, i.e., a step of pulling back the hammer manually, and a step of pulling the trigger to effect a shooting. To describe it more specifically, if the hammer is pulled back by hand, a trigger connecting rod, which is interlocked with the hammer by being connected to the lower end of the hammer, is also pulled simultaneously.
Under this condition, an engaging piece is engaged with the engaging step of the hammer, thereby effecting a loaded state. Under this loaded state, if the trigger is pulled, the trigger connecting rod pulls the engaging piece, so that the engaged state between the hammer and the engaging piece should be released. Under this condition, the hammer is rotated by the restoring force of a hammer spring, with the result that the hammer strikes the firing pin, thereby causing a bullet fired.
Meanwhile the double action is constituted such that a single step of operation effects the cartridge loading and the bullet firing. That is, if the trigger is pulled, the hammer which is connected to the trigger connecting rod is withdrawn. Then, if the trigger is pulled further, the engaging piece is pulled by the engaging step of the trigger connecting rod so as for the trigger connecting rod to be released from the engagement with the engaging step of the hammer, thereby effecting a firing of a bullet.
In the above described firing methods, the user of the pistol carries it in a state with a cartridge loaded in the firing room, and suddenly, an emergency situation may be encountered. Under such a circumstance, in the case of the single action, e.g., in the case of the 45-dia pistol M1911A1 of the Colt company of the United States, if a shooting is to be effected, the pistol should be carried in a state with the hammer withdrawn, of the pulling-back of the hammer should be precedingly carried out, before pulling the trigger.
However, if the pistol is to be carried in a state with the hammer withdrawn, its handling is extremely inconvenient, and a ambidexterous safety device has to be provided in order to prevent an accidental firing.
On the other hand, if the withdrawing of the hammer is to be carried out separately, an inconvenience is accompanied, and the pistol becomes unfit for an emergency shooting. Particularly, after continued shootings, if any further firing becomes impossible due to such as the incapacitation of the detonator striking function, then the firing can be carried out only by manually pulling back the hammer as in the case of the double action.
In an improved double action in which an attempt is made to overcome the above described disadvantages, the withdrawing of the hammer and the firing of a bullet are performed almost simultaneously only by pulling the trigger, with the advantages that any problem can be speedily remedied during the initial shooting or during an incapacitation of the striking function of the hammer. However, this has the disadvantage that too much force is required to pull the trigger, thereby deteriorating the hitting probability.